<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <div id="app">
        <input type="text" v-model="task" v-on:input="fn">
        <ul>
            <li v-for="item in arr">{{item}}</li>
        </ul>
    </div>
</body>
<script src="./js/vue.js"></script>
<script>
    Vue.config.productionTip = false

    new Vue({
        el:"#app",
        data:{
            task:"",
            arr:[]
        },
        methods:{
            fn(){
                this.arr.push(this.task);
            }
        }
    })
</script>
</html>